Electronic pen and electronic pen main body

ABSTRACT

A thin electronic pen main body is provided to enable a position detection sensor operated by a capacitance method to reliably detect pointed positions. There is provided an electronic pen main body that houses an electronic pen in a cylindrical housing in such a manner that at least a pen tip of the electronic pen may be projected from one opening of the cylindrical housing in an axial direction. The electronic pen main body includes a conductive center electrode, of which one end in the axial direction forms the pen tip, and a peripheral electrode disposed around the center electrode except at least for the pen tip, wherein the peripheral electrode is insulated from the center electrode. When the one end of the center electrode forming the pen tip is projected to the outside from the opening of the cylindrical housing upon use, a portion of the pen tip side of the peripheral electrode is also projected to the outside from the opening of the housing.

TECHNICAL FIELD

The present invention relates to an electronic pen and an electronic penmain body both operated by a capacitance method for exchanging signalswith a position detection sensor through capacitive coupling.

BACKGROUND ART

Electronic pens operated by a so-called active capacitance method havebeen commercialized as one type of electronic pen operated based on thecapacitance method. The active capacitance method allows the electronicpen to exchange signals (i.e., to interact) with a position detectionsensor of a position detection apparatus through capacitive couplingtherebetween, so that the position detection sensor may detect positionspointed to by the electronic pen.

This type of electronic pen operated by the active capacitance methodincorporates a power supply circuit that uses a primary or a secondarybattery, and a signal transmission circuit. A stylus of the electronicpen is configured with a conductor that transmits signals from thesignal transmission circuit to the position detection sensor throughcapacitive coupling (e.g., see Patent Document 1 (Japanese Patent No.5687398)).

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: Japanese Patent No. 5687398

SUMMARY OF INVENTION Technical Problem

Along with consumer preference in recent years for miniaturized devicehas come an increasing demand for mobile electronic devices that aresmaller than ever. The electronic pen is intended for use with theposition detection sensor mounted on this type of small-sized electronicdevice. Hence, there comes the demand for thinner electronic pens.

Recently, the electronic pen has been considered an extension ofstationery. There is thus a demand for modularizing the internalconfiguration of the electronic pen, so that the electronic pen may behandled in a manner similar to a ballpoint refill (a refill or acartridge). In the description that follows, what is referred to as theelectronic pen main body is a modularized part that integrates theinternal components of the electronic pen and is replaceable just like aballpoint refill.

The strength of capacitive coupling between the electronic pen and theposition detection sensor both operated by the capacitance method islower than the strength of electromagnetic induction coupling with theelectronic pen operated by the electromagnetic induction method. In acase where the electronic pen main body is configured to be a thinrefill, the strength of capacitive coupling involved is much lower. Oneproblem is that in such a state, the electronic pen main body needs tobe configured in such a manner that the positions pointed to by theelectronic pen may still be reliably detected by the position detectionsensor operated by the capacitance method.

The present invention is aimed at providing an electronic pen and anelectronic pen main body both configured to solve the above problem.

Technical Solution

In solving the above problem, there is provided an electronic pen mainbody allowing at least a pen tip of an electronic pen to be housed in acylindrical housing of the electronic pen in such a manner as to beprojectable from one opening of the cylindrical housing in an axialdirection. The electronic pen main body includes a conductive centerelectrode of which one end in the axial direction forms the pen tip, anda peripheral electrode disposed around the center electrode except atleast for the pen tip, the peripheral electrode being insulated from thecenter electrode. When the one end of the center electrode forming thepen tip is projected to the outside from the opening of the cylindricalhousing upon use, a portion of the pen tip side of the peripheralelectrode is also projected to the outside from the opening.

Further, there is provided an electronic pen having a cylindricalhousing with an opening on one end thereof forming a pen tip side in anaxial direction, the cylindrical housing holding at least one electronicpen main body inside. The electronic pen main body includes a conductivecenter electrode of which one end in the axial direction forms a pentip, and a peripheral electrode disposed around the center electrodeexcept at least for the pen tip, the peripheral electrode beinginsulated from the center electrode. When the one end of the centerelectrode forming the pen tip is projected to the outside from theopening of the cylindrical housing upon use, a portion of the pen tipside of the peripheral electrode is also projected to the outside fromthe opening.

With the electronic pen main body of the above-described configuration,the pen tip on the one end of the center electrode is projected from theopening of the electronic pen housing, and the portion of the pen tipside of the peripheral electrode is also projected from the opening ofthe electronic pen housing. As a result, a distance between the centerelectrode and the peripheral electrode of the electronic pen and theposition detection sensor operated by the capacitance method isshortened, thus ensuring superior capacitive coupling therebetween.

By use of the center electrode and the peripheral electrode of theelectronic pen main body configured as described above, it is possiblefor the position detection sensor operated by the capacitance method toreliably detect the positions pointed to by the electronic pen.

That is, a signal from the position detection sensor is received, forexample, by the peripheral electrode of the electronic pen main body. Onthe basis of the received signal, the transmission of a signal from thecenter electrode of the electronic pen main body is controlled. Thismakes it possible for the position detection sensor to reliably detectthe signal from the electronic pen main body. When the peripheralelectrode is grounded for use as a shield electrode upon signaltransmission from the center electrode, the signal can be transmittedwithout waste from the tip side (pen tip) of the center electrode. Whena signal is also transmitted from the peripheral electrode, theperipheral electrode can also be used to detect the tilt angle of theelectronic pen.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are diagrams for explaining a configuration example ofan electronic pen in a first embodiment of the present invention.

FIGS. 2A-2C are diagrams for explaining a configuration example of anelectronic pen main body in the first embodiment of the presentinvention.

FIGS. 3A and 3B are diagrams for explaining a configuration example of apen tip of the electronic pen main body in the first embodiment of thepresent invention.

FIGS. 4A and 4B are diagrams for explaining the configuration example ofthe electronic pen main body in the first embodiment of the presentinvention.

FIG. 5 is a block diagram for explaining a configuration example ofelectronic circuits in the electronic pen main body in the firstembodiment of the present invention.

FIGS. 6A-6D are diagrams for explaining the workings of theconfiguration example of the electronic circuits in the electronic penmain body in the first embodiment of the present invention.

FIG. 7 is a diagram for explaining a configuration example of a positiondetection apparatus operated by the capacitance method and used inconjunction with the electronic pen in the first embodiment of thepresent invention.

FIGS. 8A-8F are diagrams for explaining a method of detecting a tiltangle of the electronic pen with respect to the position detectionapparatus in the example of FIG. 7.

FIG. 9 is a diagram for explaining a configuration example of anelectronic pen in a second embodiment of the present invention.

FIGS. 10A-10C are diagrams for explaining a configuration example of anelectronic pen main body for use with an electronic pen in a thirdembodiment of the present invention.

FIGS. 11A and 11B are diagrams for explaining a configuration example ofthe electronic pen in the third embodiment of the present invention.

FIGS. 12A-12C are diagrams for explaining configuration examples ofelectronic pen main bodies in other embodiments of the presentinvention.

DETAILED DESCRIPTION

Some embodiments of an electronic pen and an electronic pen main bodyaccording to the present invention are described below with reference tothe accompanying drawings.

First Embodiment

An electronic pen in a first embodiment is configured to detachably holda cartridge-type electronic pen main body inside a cylindrical housingof the electronic pen.

Some electronic pens introduced in recent years and operated by theactive capacitance method are of an interactive communication type thatreceives signals from a position detection sensor detecting positionspointed to by the electronic pen and transmits signals in a format basedon the demand of the received signals.

For this type of interactive communicative electronic pen, what isimportant is the location of a reception part that receives signals fromthe position detection sensor. In the case of the electronic penoperated by the capacitance method, signals transmitted from theposition detection sensor form an electric field that can be receivedthrough capacitive coupling. A reaching distance of such signals is thussignificantly small. For this reason, the reception part of theinteractive communicative electronic pen needs to be located near thepen tip so as to be able to receive signals with high strength from theposition detection sensor.

The electronic pen of this embodiment thus has its main body optimallyconfigured for use in conjunction with the above-described interactivecommunicative electronic pen. That is, in the embodiment to be describedbelow, the electronic pen main body includes a reception part thatreceives signals from the position detection sensor. The reception partis configured to have a center electrode formed of an electricallyconducting material, wherein the center electrode is electricallyinsulated from, and surrounded up to its tip by, a peripheral electrodeformed of a cylindrical conductor.

Recently, it has been proposed that the tilt angle of the electronic penrelative to a position detection sensor surface (i.e., the angle formedbetween the axial direction of the electronic pen and the positiondetection sensor surface; simply referred to as the tilt angle of theelectronic pen hereunder) should be detected by a position detectionapparatus and that the detected tilt angle should be reflected, forexample, in the thickness and other characteristics of a pointing path(writing path) of the electronic pen. In the electronic pen main body ofthis embodiment, the above-described peripheral electrode is furtherconfigured for use in detecting the tilt angle of the electronic pen.

In the first embodiment, the peripheral electrode is also configured toact as a shield electrode with respect to the center electrode thattransmits a position detection signal.

FIG. 1 is a set of diagrams depicting a configuration example of anelectronic pen in the first embodiment of the present invention. Theelectronic pen 1 of the first embodiment has a hollow part 2 a in acylindrical housing 2 (called the pen housing 2 hereunder) that holds anelectronic pen main body 3. A knock cam mechanical part 4 provides aknock type structure that allows the pen tip of the electronic pen mainbody 3 to be projected from and retracted into an opening 2 b on one endside of the pen housing 2 in a longitudinal direction.

FIG. 1A depicts a state in which the electronic pen main body 3 as awhole is housed in the hollow part 2 a in the pen housing 2. FIG. 1Bdepicts a state in which the pen tip of the electronic pen main body 3is projected from the opening 2 b of the pen housing 2 by the knock cammechanical part 4. In the example of FIG. 1, the pen housing 2 of theelectronic pen 1 is assumed to be configured with a transparentsynthetic resin that allows the inside to be seen through.

The electronic pen 1 of this embodiment is configured to be replaceablewith commercially available knock type ballpoint pens.

The pen housing 2 and the knock cam mechanical part 4 held therein areconfigured to be structurally and dimensionally identical to those ofcommon knock type ballpoint pens that are commercially available.

As depicted in FIG. 1, the knock cam mechanical part 4 has a knownconfiguration in which a cam main body 41, a knocking rod 42, and arotator 43 are combined with one another. The cam main body 41 is formedon an inner wall surface of the cylindrical pen housing 2. An end part42 a of the knocking rod 42 is projected from an opening 2 c opposite tothe pen tip side of the pen housing 2, the knocking rod 42 therebyallowing a user to perform knocking operations on its end part 42 a. Therotator 43 has a fitting part 43 a fitted to the other end part of theelectronic pen main body 3 opposite to its pen tip side.

It is to be noted that the fitting part 43 a is different from that ofthe housing of an ordinary knock type ballpoint pen in that the fittingpart 43 a is additionally configured for electrical connection with theelectronic pen main body 3. That is, as will be discussed later, theelectronic pen main body 3 has an internal signal transmission circuitthat generates signals to be transmitted via the center electrode orperipheral electrode to the position detection sensor, and the signaltransmission circuit needs a power voltage supply.

In this embodiment, as will be discussed later, the electronic pen mainbody 3 includes the signal transmission circuit and an internalelectrical storage element that supplies power thereto. The electricalstorage element needs to be charged from outside of the electronic penmain body 3. For this purpose, the end part fitted to the fitting part43 a of the electronic pen main body 3 in this embodiment is furnishedwith a terminal conductor (electrode) connected to the above-describedelectrical storage element. The fitting part 43 a thus forms aconducting body that connects with the terminal conductor connected tothe electrical storage element. It is to be noted that, except for itselectrical arrangements, the structure for coupling with the electronicpen main body 3 remains the same as that in which a ballpoint refill iscoupled and fitted. A configuration example of the end part fitted tothe fitting part 43 a of the electronic pen main body 3 will bediscussed later along with a configuration example of the fitting part43 a.

What makes the pen housing 2 different from that of the knock typeballpoint pen as a writing instrument is that as depicted in FIG. 1,charging electrodes 2 d and 2 e connected to the conductor in thefitting part 43 a are formed on an outer peripheral side surface of thepen housing 2 opposite to the pen tip side in this example.

When the electronic pen 1 configured as described above is in the stateof FIG. 1A, pressing the end part 42 a of the knocking rod 42 causes theknock cam mechanical part 4 to lock the electronic pen main body 3 intothe state of FIG. 1B in the pen housing 2, with the pen tip of theelectronic pen main body 3 projected from the opening 2 b of the penhousing 2. In the state of FIG. 1B, again pressing the end part 42 a ofthe knocking rod 42 causes the knock cam mechanical part 4 to unlock theelectronic pen main body 3. A return spring 5 brings the electronic penmain body 3 in the pen housing 2 back to the position in the state ofFIG. 1A. The detailed configurations and the workings of the knock cammechanical part 4 are well known and thus will not be explained further.

Embodiment of the Electronic Pen Main Body 3

FIG. 2 is a set of diagrams depicting a configuration example of theelectronic pen main body 3 in comparison with a refill of a commerciallyavailable knock type ballpoint pen. That is, FIG. 2A depicts a ballpointrefill 6 of a commercially available knock type ballpoint pen, and FIG.2B illustrates a configuration example of the electronic pen main body 3of this embodiment. In this embodiment, as will be discussed later, theelectronic pen main body 3 is configured to be dimensionally similar tothe knock ballpoint refill 6 and thus replaceable with the latter.

FIG. 3 is a set of diagrams depicting a configuration example of the pentip side of the electronic pen main body 3 of this embodiment. FIG. 3Aillustrates an appearance of the pen tip side, and FIG. 3B gives alongitudinal sectional view of the pen tip side. Also, FIG. 4 is a setof exploded perspective views for explaining a configuration example ofthe pen tip side of the electronic pen main body 3 in this embodimentillustrated in FIG. 3.

As depicted in FIG. 2A, the refill 6 of a commercially available knocktype ballpoint pen has a known configuration in which a pen tip part 61tipped with a ball and a cylindrical ink storage part 62 of apredetermined outer diameter are integrally coupled with each other viaa cylindrical coupling part 63 of a predetermined outer diameter. Thepen tip part 61 is cylindrically shaped and is tapered toward the tipend. A maximum outer diameter R1 of the pen tip part 61 is made smallerthan a diameter R0 of the opening 2 b of the pen housing 2. The couplingpart 63 and the ink storage part 62 have the same outer diameter R2,which is set to be slightly larger than the maximum outer diameter R1 ofthe pen tip part 61. For example, the outer diameter R2 is set to be 2.2millimeters. It is to be noted that the diameter R0 of the opening 2 bof the pen housing 2 is subject to the dimensional relations ofR1<R0<R2.

As depicted in FIG. 2B and in FIGS. 3A and 3B, the electronic pen mainbody 3 of this embodiment has a housing 30 (called the main body housing30 hereunder) configured in such a manner that the pen tip side of amain body cylindrical part 31 is coupled with a peripheral electrode 33made of a conductive member, such as conductive metal, via a cylindricalcoupling member 32.

In this example, as depicted in FIG. 2B, the main body cylindrical part31 is configured with a resin pipe part 31 b coupled with a metal pipepart 31 a at the rear end side opposite to the pen tip side. In the mainbody cylindrical part 31 of this example, the pen tip side of the metalpipe part 31 a is coupled with the peripheral electrode 33 via thecylindrical coupling member 32. The cylindrical coupling member 32 alsofunctions as an insulator between the metal pipe part 31 a and theperipheral electrode 33. The end part of the electronic pen main body 3on the side of the resin pipe part 31 b forms a fitting part fitted tothe fitting part 43 a in the pen housing 2.

In this example, as depicted in FIGS. 2 and 3, the peripheral electrode33 is shaped to have a cylindrical shaped part 33 a of the predeterminedouter diameter R2 and a tapered part 33 b tapered toward the pen tipside. The metal pipe part 31 a of the main body cylindrical part 31 hasa cylindrical shape with the same outer diameter as the outer diameterR2 of the cylindrical shaped part 33 a of the peripheral electrode 33.

The cylindrical coupling member 32 is constituted by an insulatingmaterial, which is a resin in this example. The cylindrical couplingmember 32 is a cylindrical body as depicted in FIG. 3B. Approximately inthe middle of an outer peripheral surface of the cylindrical couplingmember 32 in the axial direction, there is a ring-shaped flange part 32Fprojected from the outer peripheral surface in a direction perpendicularto the axial direction. The ring-shaped flange part 32F has apredetermined width W (see FIG. 3) in the axial direction. The edge faceof the flange part 32F is configured to be an integral part of the mainbody housing 30 flush with the main body cylindrical part 31 and theperipheral electrode 33 with no level differences therebetween, asdepicted in FIGS. 3A and 3B. That is, the outer periphery diameter ofthe ring-shaped flange part 32F is selected to be the same as the outerdiameter of the peripheral electrode 33 and of the metal pipe part 31 aof the main body cylindrical part 31.

The cylindrical coupling member 32 on the pen tip side of thering-shaped flange part 32F in the axial direction forms a firstcylindrical fitting part 32 a fitted to the cylindrical shaped part 33 aof the peripheral electrode 33. The outer diameter of the firstcylindrical fitting part 32 a of the cylindrical coupling member 32 ismade equal to or slightly smaller than the inner diameter of thecylindrical shaped part 33 a of the peripheral electrode 33. Thecylindrical shaped part 33 a of the peripheral electrode 33 isconfigured to be pressed in up to the ring-shaped flange part 32F andcoupled with the first cylindrical fitting part 32 a of the cylindricalcoupling member 32.

The cylindrical coupling member 32 on the rear end side of thering-shaped flange part 32F in the axial direction forms a secondcylindrical fitting part 32 b fitted to the metal pipe part 31 a of themain body cylindrical part 31. The outer diameter of the secondcylindrical fitting part 32 b of the cylindrical coupling member 32 ismade equal to or slightly smaller than the inner diameter of the metalpipe part 31 a of the main body cylindrical part 31. The metal pipe part31 a of the main body cylindrical part 31 is configured to be pressed inup to the ring-shaped flange part 32F and coupled with the secondcylindrical fitting part 32 b of the cylindrical coupling member 32.

In the state where the metal pipe part 31 a of the main body cylindricalpart 31 and the peripheral electrode 33 are inserted in and fitted tothe cylindrical coupling member 32, a single cylindrical main bodyhousing 30 is formed as depicted in FIG. 2B and in FIGS. 1A and 1B. Atthis point, as discussed above, the outer peripheral surface of themetal pipe part 31 a of the main body cylindrical part 31, the outerperipheral surface of the peripheral electrode 33, and the edge face ofthe ring-shaped flange part 32F of the cylindrical coupling member 32are flush with each other. The metal pipe part 31 a of the main bodycylindrical part 31 and the peripheral electrode 33, both made of anelectrically conducting material, are electrically separated (i.e.,insulated) from each other with no contact therebetween due to thepresence of the ring-shaped flange part 32F of the cylindrical couplingmember 32.

Inside the main body housing 30 is a hollow part 30 a as depicted inFIG. 3B. The pen tip side of the peripheral electrode 33 of the mainbody housing 30 is fitted with a front cap 34 made of an insulatingmaterial, as depicted in FIG. 2B and in FIGS. 3A and 3B. The front cap34 has, at its tip, an opening 34 a (see FIG. 3B) with a diameter largerthan the diameter of a center electrode 35. The opening 34 acommunicates with the hollow part 30 a of the main body housing 30.

The center electrode 35 forms the stylus of the electronic pen main body3 of this embodiment. In this example, the center electrode 35 is aconductive member, which is formed of a conductive metal. As depicted inFIG. 3B, the center electrode 35 is inserted from the opening 34 a ofthe front cap 34 into the main body housing 30 in such a manner that theend part opposite to the pen tip side is detachably fitted to a stylusholding member 7, to be described later.

The stylus 35 and the peripheral electrode 33, both made of anelectrically conducting material, are electrically separated (i.e.,insulated) from each other by the front cap 34 as an insulatingmaterial, as depicted in FIG. 3B. In the electronic pen main body 3 ofthis embodiment, with the center electrode 35 attached thereto, theperipheral electrode 33 is arranged to surround the center electrode 35on the rear end side thereof away from a pen tip part 35 a forming thepen tip of the center electrode 35, as depicted in FIG. 3B. It is to benoted that, in the description that follows, the center electrode 35will be referred to as the stylus 35.

In this example, as depicted in FIGS. 2A and 2B, the pen tip side of theelectronic pen main body 3 is configured to be approximately equaldimensionally to the pen tip side of the ballpoint refill 6. That is,the outer diameter of the main body cylindrical part 31 in the main bodyhousing 30 and the diameter of the cylindrical shaped part 33 a of theperipheral electrode 33 are each equal to the outer diameter R2 of theink storage part 62 and coupling part 63 of the refill 6 in acommercially available knock type ballpoint pen, as depicted in FIG. 2B.

The tapered part 33 b of the peripheral electrode 33 of the main bodyhousing 30 on the tip side thereof is gradually tapered toward the pentip. In this embodiment, as depicted in FIG. 2B, the pen tip side of thetapered part 33 b away from the approximate middle thereof in the axialdirection is arranged not to exceed the diameter R0 of the opening 2 bof the pen housing 2 on the pen tip side.

With the stylus 35 inserted in and fitted to the electronic pen mainbody 3 through the opening 34 a of the front cap 34, the length from thetip of the stylus 35 to the position where the outer diameter of thetapered part 33 b of the peripheral electrode 33 attains the diameter R1is arranged to be approximately equal to a length L1 of the pen tip part61 of the refill 6 of a commercially available knock type ballpoint penin the axial direction.

The length (total length) of the electronic pen main body 3 with thestylus 35 attached thereto is selected to be equal to a total length L2of the ballpoint refill 6, as depicted in FIGS. 2A and 2B.

The electronic pen main body 3 configured as described above is housedin the pen housing 2 when the main body cylindrical part 31 is fitted tothe fitting part 43 a of the rotator 43 in the knock cam mechanical part4. With the electronic pen 1 of this embodiment, the user presses theend part 42 a of the knocking rod 42 when used in conjunction with aposition detection apparatus. The pressing action causes the electronicpen 1 to extend, from the opening 2 b of the pen housing 2, the pen tippart 35 a of the stylus 35, a portion of the front cap 34, and a portionof the tapered part 33 b of the peripheral electrode 33 on the pen tipside, as depicted in FIG. 1B.

That is, this embodiment is configured in such a manner that not onlythe tip of the stylus 35 attached to the electronic pen main body 3 butalso a portion of the pen tip side of the peripheral electrode 33surrounding the stylus 35 is projected outside from the opening 2 b ofthe pen housing 2 of the electronic pen 1, as depicted in FIG. 1B. Inthis state, the user of the electronic pen 1 performs input operationsto point to desired positions on the position detection sensor of theposition detection apparatus.

After using the electronic pen 1, the user can again press the end part42 a of the knocking rod 42 to bring the entire electronic pen main body3 into the hollow part 2 a of the pen housing 2, as depicted in FIG. 1A.At this point, the electronic pen main body 3 as a whole is accommodatedinside the hollow part 2 a of the pen housing 2 in such a manner thatthe pen tip part 35 a of the stylus 35 in the electronic pen main body 3is protected by the pen housing 2.

Inside the hollow part 30 a of the main body housing 30, as indicated bydotted lines in FIG. 2B and in FIG. 3A, there are provided the stylusholding member 7, a writing pressure detection part 8, a printed-circuitboard 9 including a signal transmission circuit, and a capacitor 10 as atypical electrical storage element for supplying power voltage, arrangedin that order away from the pen tip side in the axial direction.

In this embodiment, the hollow part 30 a of the main body housing 30holds a substrate holder 300 having a substrate placing table 301 onwhich the printed-circuit board 9 is placed, as depicted in FIG. 3B.

The substrate holder 300 is formed of an insulating resin. In thelongitudinal direction of the electronic pen main body 3, i.e., in theaxial direction thereof, the substrate holder 300 has a writing pressuredetection part holder 302 that holds the writing pressure detection part8 on the opposite side of the substrate placing table 301. As depictedin FIG. 3B, the substrate holder 300 in the hollow space of the mainbody housing 30 is configured in such a manner that the writing pressuredetection part holder 302 and the substrate placing table 301 arearranged continuously in the longitudinal direction of the electronicpen main body 3, i.e., in the axial direction thereof. The writingpressure detection part holder 302 has a cylindrical shape with aninternal hollow space that holds multiple components of the writingpressure detection part 8. The substrate placing table 301 is shapedlike a boat on which the printed-circuit board 9 is placed and retained.As such, the substrate placing table 301 is shaped as if a cylindricalbody were cut approximately in half in the axial direction.

The substrate holder 300 is held inside the main body housing 30 in sucha manner that the writing pressure detection part holder 302 is orientedtoward the pen tip side. The writing pressure detection part 8 retainedby the writing pressure detection part holder 302 is coupled with astylus holding member 7 fitted to the stylus 35 to hold it in such amanner that the pressure (i.e., writing pressure) applied to the stylus35 is transmitted to the writing pressure detection part 8.

In this embodiment, the outer diameter of the writing pressure detectionpart holder 302 of the substrate holder 300 is selected to be equal toor slightly smaller than the outer diameter of the second cylindricalfitting part 32 b of the cylindrical coupling member 32. As depicted inFIG. 3B, a portion of the writing pressure detection part holder 302 inthe substrate holder 300 is fitted to a portion of the secondcylindrical fitting part 32 b of the cylindrical coupling member 32.This allows the writing pressure detection part holder 302 of thesubstrate holder 300 to be coupled with the second cylindrical fittingpart 32 b of the cylindrical coupling member 32.

As depicted in FIG. 3B, the substrate holder 300 is positionallyrestricted from moving in the axial direction in the main body housing30 when the writing pressure detection part holder 302 is fitted to andcoupled with the second cylindrical fitting part 32 b of the cylindricalcoupling member 32 in the axial direction.

Although not illustrated, on the substrate placing table 301 of thesubstrate holder 300, both ends of the capacitor 10 disposed on theopposite side of the writing pressure detection part holder 302 areelectrically connected with a copper foil pattern comprising the powersupply line and the ground line of the printed-circuit board 9. Thisallows the voltage of the capacitor 10 to be supplied as a power supplyvoltage to the circuits formed on the printed-circuit board 9.

In this embodiment, the metal pipe part 31 a of the main bodycylindrical part 31 made of an electrically conducting material isconnected electrically with the copper foil pattern of the ground lineof the printed-circuit board 9.

In this embodiment, the printed-circuit board 9 includes a circuitsection constituted by an IC (Integrated Circuit) 100 (see FIGS. 3A and3B) and by peripheral circuit components thereof. The IC 100 forms asignal transmission circuit generating signals to be output from thestylus 35 and peripheral electrode 33, and a control circuit controllingthe signal transmission from the signal transmission circuit to thestylus 35 and peripheral electrode 33. Although not depicted, theperipheral circuit section includes a charging circuit for the capacitor10. The charging circuit for the capacitor 10 may alternatively beprovided outside of the electronic pen 1.

The stylus holding member 7 fitted to and holding the stylus 35 isconfigured with a conductive elastic member 71, a stylus holder 72, acoil spring 73, and a conductor terminal member 74 as depicted in FIG.3B and in FIG. 4. In this embodiment, as depicted in FIG. 3B, the stylus35 is fitted to and held by the stylus holder 72, which is made of anelectrically conducting material, via the conductive elastic member 71.The stylus holding member 7 also functions as a transmission membertransmitting the writing pressure applied to the stylus 35 to thewriting pressure detection part 8.

With the stylus holder 72 fitted to a holding member 83 of the writingpressure detection part 8 held by the writing pressure detection partholder 302, the pressure (i.e., writing pressure) applied to the stylus35 is transmitted to the writing pressure detection part 8. In thiscase, the stylus holder 72 is continuously pressed against the substrateholder 300 toward the stylus 35 by a coil spring 73. The coil spring 73,which is interposed between the stylus holder 72 and the substrateholder 300, is an elastic member formed of an electrically conductingmaterial such as a conductive metal. Incidentally, the coil spring 73,along with the conductor terminal member 74, constitutes an electricalconnection member for transmitting to the stylus 35 the signals from theIC 100 disposed on the printed-circuit board 9.

FIG. 4A is an exploded perspective view depicting the stylus 35, theconductive elastic member 71, the coil spring 73, the conductor terminalmember 74, and the writing pressure detection part holder 302 of thesubstrate holder 300.

The conductive elastic member 71, typically made of a conductive rubber,is formed in a cylindrical shape with a through-hole 71 a into which theend part of the stylus 35 opposite to its pen tip part 35 a is fitted. Aportion of the conductive elastic member 71 on the side of the stylus 35is smaller in outer diameter and thinner-walled than the remainingportion. Also, this portion of the conductive elastic member 71constitutes a grip part 711 with a slit 712 formed therein to readilygrip the stylus 35.

In the above-described configuration, the stylus 35 is gripped by twothin-walled arcuate portions with the slit 712 formed thereby in thegrip part 711. This allows the stylus 35 to be readily inserted into thegrip part 711 of the conductive elastic member 71. When pulled by apredetermined force, the stylus 35 is easily extracted from theconductive elastic member 71.

The stylus holder 72 is made of an electrically conducting material suchas SUS (Steel Special Use Stainless). The stylus holder 72 is formed byan integral combination of a holder fitting part 721 and a rod-like part722. The holder fitting part 721 has a recessed hole 721 a for holdingand fitting the conductive elastic member 71. The rod-like part 722 isfitted to the holding member 83, to be discussed later, of the writingpressure detection part 8.

After the conductive coil spring 73 is attached to the rod-like part 722of the stylus holder 72 holding the conductive elastic member 71 asdescribed above, the rod-like part 722 of the stylus holder 72 is fittedto the holding member 83 of the writing pressure detection part 8 heldby the writing pressure detection part holder 302 of the substrateholder 300.

In this case, for the electronic pen main body 3 of this embodiment, itis necessary to consider that the transmission signal generated bycircuits on the printed-circuit board 9 needs to be supplied to thestylus 35. However, since the holding member 83 of the writing pressuredetection part 8 held in the writing pressure detection part holder 302of the substrate holder 300 is made of an insulating resin, noelectrical connection can be established between the stylus holder 72and the holding member 83.

Thus, in this embodiment, an electrical connection member is constitutedby the coil spring 73 made of an electrically conducting material andinterposed between the stylus holder 72 and the writing pressuredetection part holder 302 of the substrate holder 300, and by theconductor terminal member 74 disposed in the writing pressure detectionpart holder 302 of the substrate holder 300. This electrical connectionmember establishes electrical connection enabling the supply of signalsfrom the signal transmission circuit on the printed-circuit board 9.

That is, in this embodiment, the writing pressure detection part holder302 of the substrate holder 300 is furnished with the conductor terminalmember 74 made of an electrically conducting material such as SUS, insuch a manner that the conductor terminal member 74 covers an opening302 a through which the rod-like part 722 of the stylus holder 72 isinserted, as depicted in FIG. 4A.

The conductor terminal member 74 has an abutting plate part 741 with athrough-hole 741 a covering the opening 302 a of the writing pressuredetection part holder 302 of the substrate holder 300, wherein thethrough-hole 741 a allows the rod-like part 722 of the stylus holder 72to be inserted, as depicted in FIGS. 4A and 4B.

An extension part 742 spanning the writing pressure detection partholder 302 of the substrate holder 300 is extended up to the substrateplacing table 301. In the state where the conductor terminal member 74is attached to the writing pressure detection part holder 302 of thesubstrate holder 300, a terminal part 742 a at the end of the extensionpart 742 extended from the conductor terminal member 74 abuts againstand is, for example, soldered to a conductor on the back side of theprinted-circuit board 9 disposed on the substrate placing table 301 ofthe substrate holder 300, as depicted in FIG. 3B. This provideselectrical connection between the conductor terminal member 74 and thesignal transmission circuit disposed on the printed-circuit board 9.

The rod-like part 722 of the stylus holder 72 fitted with the conductiveelastic member 71 is inserted via the through-hole 741 a of the abuttingplate part 741 of the conductor terminal member 74 into the hollow spaceof the writing pressure detection part holder 302 of the substrateholder 300. The rod-like part 722 is fitted to the writing pressuredetection part holder 302 with the coil spring 73 interposedtherebetween. The inner diameter of the coil spring 73 is made largerthan the outer diameter of the rod-like part 722 of the stylus holder72.

The coil spring 73 thus comes into elastic contact with the stylusholder 72, and abuts against the abutting plate part 741 of theconductor terminal member 74 for elastic contact therewith. Because thecoil spring 73 is formed by an electrically conducting material andbecause the conductive elastic member 71 and the stylus holder 72 areboth conductive, the conductive elastic member 71 fitted to the stylusholder 72 is connected electrically to the circuit section on theprinted-circuit board 9 via the coil spring 73 and the conductorterminal member 74.

The stylus 35 is inserted in and fitted to the through-hole 71 a of theconductive elastic member 71 fitted to the stylus holder 72 housed inthe main body housing 30 as described above. The stylus 35 is thus heldin the stylus holder 72 via the conductive elastic member 71. In thisstate, the stylus 35 is electrically connected to the signaltransmission circuit on the printed-circuit board 9. The stylus 35 isthus supplied with signals coming from the signal transmission circuit.

Explained next is how the writing pressure detection part holder 302 ofthe substrate holder 300 and the writing pressure detection part 8 areconfigured, along with how the holding member 83 of the writing pressuredetection part 8 is fitted to the stylus holder 72.

A writing pressure detection module is formed by the writing pressuredetection part 8 being held in the writing pressure detection partholder 302 as depicted in FIG. 3B. When the stylus 35 is coupled to thewriting pressure detection module via the stylus holder 72, the writingpressure applied to the pen tip part 35 a of the stylus 35 is detectedby the writing pressure detection part 8 in the writing pressuredetection module. In this case, the writing pressure detection moduledetects the writing pressure when some of the components of the writingpressure detection part 8 constituting the module are axially movedtogether with the stylus 35 and the stylus holder 72.

The writing pressure detection part 8 of this example uses a variablecapacitor of which the capacitance varies with the writing pressureapplied to the stylus 35. As depicted in FIG. 3B, the writing pressuredetection part 8 is formed of multiple components including a dielectricbody 81, a terminal member 82, a holding member 83, a conductive member84, and an elastic member 85.

In the state where the stylus holder 72 is fitted to the writingpressure detection part holder 302 of the substrate holder 300 asdescribed above, the stylus 35 is pressed into the through-hole 71 a ofthe conductive elastic member 71 fitted to the stylus holder 72. Thiscauses the stylus 35 to be securely held in the stylus holder 72 bymeans of the conductive elastic member 71 as discussed above. It is tobe noted that, in the state in which the stylus 35 is fitted to and heldby the stylus holder 72, it is possible to extract the stylus 35 in thedirection of the pen tip part 35 a for replacement as explained above.

In the electronic pen main body 3, a pressure applied to the pen tippart 35 a of the stylus 35 causes the stylus 35 to be axially displacedtoward the rear end side in keeping with the pressure. The displacementin turn causes the holding member 83 in the writing pressure detectionpart holder 302 to be displaced toward the dielectric body 81 against abiasing force of the elastic member 85. As a result, the conductivemember 84 fitted to the holding member 83 is displaced toward thedielectric body 81. A distance between the conductive member 84 and thedielectric body 81, as well as the contact area therebetween, variesaccording to the pressure applied to the stylus 35.

Consequently, the capacitance of the variable capacitor formed betweenthe terminal member 82 constituting a first electrode on one hand andthe conductive member 84 constituting a second electrode on the otherhand varies with the pressure applied to the stylus 35. Changes in thecapacitance of the variable capacitor are detected by the IC 100disposed on the printed-circuit board 9, thus allowing the writingpressure to be detected.

It is to be noted that the configuration of the writing pressuredetection part 8 is not limited to what has been described above.Alternatively, the writing pressure detection part 8 may utilize avariable capacitor configured with a semiconductor chip made of MEMS(Micro Electro Mechanical Systems) elements (e.g., see Patent Document(Japanese Patent Laid-Open No. 2013-161307)).

Explained next is the electrical connection between the peripheralelectrode 33 and the circuit section of the printed-circuit board 9. Theouter peripheral surface of the cylindrical coupling member 32 has arecessed groove (not depicted) formed in the axial direction of thecylindrical coupling member 32 extending from the first cylindricalfitting part 32 a to the second cylindrical fitting part 32 b past theunderside of the ring-shaped flange part 32F.

The outer peripheral side surface of the writing pressure detection partholder 302 in the substrate holder 300 also has a recessed groove (notdepicted) formed to continue from the recessed groove of the secondcylindrical fitting part 32 b. In this continuous recessed groove, aconnection terminal conductor 11 made of an electrically conductingmaterial, such as a conductive metal in this example, is disposed asdepicted in FIG. 3B. An end part 11 a of the connection terminalconductor 11 placed in the recessed groove of the cylindrical couplingmember 32 on the side of the first cylindrical fitting part 32 a isslightly swelled at least partially from the outer peripheral surface ofthe first cylindrical fitting part 32 a, as depicted in FIG. 3B. It isto be noted that the recessed groove at the end part 11 a is formed at adepth such that the end part 11 a can be elastically pushed down whenpressed from above.

As a result, when the peripheral electrode 33 is fitted to the firstcylindrical fitting part 32 a of the cylindrical coupling member 32, theend part 11 a of the connection terminal conductor 11 comes into securecontact with the inner wall of the peripheral electrode 33. Thisestablishes electrical connection between the peripheral electrode 33and the connection terminal conductor 11. As depicted in FIG. 3B, an endpart 11 b of the connection terminal conductor 11 extending toward theprinted-circuit board 9 is electrically connected to the back side 9 bof the printed-circuit board 9. Although not illustrated, the end part11 b of the connection terminal conductor 11 is electrically connectedvia through-holes to the circuit section of the printed-circuit board 9on the front side thereof.

It is to be noted that the recessed groove in which the connectionterminal conductor 11 is disposed has a depth such that when the metalpipe part 31 a of the main body cylindrical part 31 is fitted to thesecond cylindrical fitting part 32 b, the connection terminal conductor11 and the metal pipe part 31 a are not in contact with each other.Alternatively, an insulating material may be interposed between theconnection terminal conductor 11 and the metal pipe part 31 a.

Explained next with reference to FIG. 2C is a configuration exampleregarding the rear end side of the electronic pen main body 3 oppositeto the pen tip side and the fitting part 43 a of the main body housing30. In this example, a resin pipe part 31 b forms the side of the mainbody cylindrical part 31 of the main body housing 30, wherein the sideis fitted to the fitting part 43 a of the rotator 43 in the knock cammechanical part 4 of the pen housing 2 of the electronic pen 1. Theresin pipe part 31 b is furnished with a pair of terminal conductorsconnected to both ends of the capacitor 10. A corresponding pair ofconductors are formed on the fitting part 43 a of the rotator 43 in theknock cam mechanical part 4 of the pen housing 2 of the electronic pen1. The paired conductors are electrically connected to the chargingelectrodes 2 d and 2 e formed, in this example, on the outer peripheralside surface of the pen housing 2 opposite to the pen tip side.

FIG. 2C is an enlarged sectional view for explaining a configuration inwhich the resin pipe part 31 b of the main body cylindrical part 31 ofthe electronic pen main body 3 is coupled with the fitting part 43 a ofthe main body cylindrical part 31 of the main body housing 30.

As depicted in FIG. 2C, the fitting part 43 a has a cylindrical recessedpart 431 fitted with the resin pipe part 31 b. A center portion of thecylindrical recessed part 431 is furnished with a center rod-like part432 inserted into a hollow space of the resin pipe part 31 b. In thisexample, the diameter of the cylindrical recessed part 431 of thefitting part 43 a is made slightly larger than the outer diameter of theresin pipe part 31 b in such a manner that when the resin pipe part 31 bis fitted to the fitting part 43 a, the outer peripheral side surface ofthe resin pipe part 31 b comes into contact with the inner wall surfaceof the cylindrical recessed part 431 of the fitting part 43 a.Furthermore, this configuration is such that when the resin pipe part 31b is fitted to the fitting part 43 a, an inner peripheral side surfaceof the resin pipe part 31 b comes into contact with an outer peripheralside surface of the center rod-like part 432 in the cylindrical recessedpart 431 of the fitting part 43 a.

As depicted in FIG. 2C, a terminal conductor 12 is deposited on theouter peripheral side surface of the resin pipe part 31 b of the mainbody cylindrical part 31, wherein the terminal conductor 12 iselectrically connected to one electrode terminal 10 a of the capacitor10 housed in the main body cylindrical part 31. A terminal conductor 13is deposited on the inner wall surface of the resin pipe part 31 b ofthe main body cylindrical part 31, wherein the terminal conductor 13 iselectrically connected to the other electrode terminal 10 b of thecapacitor 10. The terminal conductors 12 and 13 are electricallydisconnected from each other.

Meanwhile, a conductor 14 is formed on the inner wall surface of thecylindrical recessed part 431 of the fitting part 43 a, wherein theconductor 14 is electrically connected to the charging electrode 2 dprovided in the pen housing 2. A conductor 15 is formed on the outerperipheral side surface of the center rod-like part 432 in thecylindrical recessed part 431 of the fitting part 43 a, wherein theconductor 15 is connected to the charging electrode 2 d provided in thepen housing 2. The conductors 14 and 15 are electrically disconnectedfrom each other.

In this case, the terminal conductors 12 and 13 of this example areformed all over the outer peripheral side surface and inner wallsurface. The conductors 14 and 15 of the fitting part 43 a are alsoformed all over the inner wall surface of the cylindrical recessed part431 and over the entire outer peripheral side surface of the centerrod-like part 432. This makes it possible for the terminal conductors 12and 13 of the electronic pen main body 3 and the conductors 14 and 15 ofthe fitting part 43 a to be electrically connected with each other whenthe end part of the resin pipe part 31 b in the main body cylindricalpart 31 of the electronic pen main body 3 is fitted to the fitting part43 a, regardless of the rotation angle at which the fitting is made.Incidentally, it is not necessary for the conductors 12, 13, 14, and 15to be formed over the entire circumference in the circumferentialdirection. Regardless of the rotation angle at which the fitting isestablished, the terminal conductors 12 and 13 of the electronic penmain body 3 and the conductors 14 and 15 of the fitting part 43 a areallowed to have some missing portions in their circumferential directionas long as they are electrically connected with each other.

In the above configuration in which the electronic pen main body 3 isfitted to the fitting part 43 a of the rotator 43 in the knock cammechanical part 4 of the pen housing 2 of the electronic pen 1, bothends of the capacitor 10 housed in the electronic pen main body 3 areconnected with the charging electrodes 2 d and 2 e of the pen housing 2of the electronic pen 1. This allows the capacitor 10, when devoid ofstored supply power voltage, to be charged with a sufficient supplypower voltage via the charging electrodes 2 d and 2 e.

Electronic Circuit Configuration Example of the Electronic Pen Main Body3

FIG. 5 depicts an electrical configuration example of the electronic penmain body 3 of this embodiment. In this example, as depicted in FIG. 5,the IC 100 disposed on the printed-circuit board 9 constitutes a controlcircuit 101. The control circuit 101 is connected with a signaltransmission circuit 102 and a signal reception circuit 103. The controlcircuit 101 is further connected with a variable capacitor 8C formed bythe writing pressure detection part 8. The variable capacitor 8C isconnected in parallel with a resistor 8R.

A signal output end of the signal transmission circuit 102 is connectedto the stylus 35 via a switch circuit 104. In this case, the conductorterminal member 74, the stylus holder 72, and the conductive elasticmember 71 are interposed between the stylus 35 and the switch circuit104 as described above.

Also in this example, the signal output end of the signal transmissioncircuit 102 is connected to a terminal S of a selector switch circuit105. A movable terminal M of the selector switch circuit 105 isconnected to the peripheral electrode 33. In this case, the connectionterminal conductor 11 is interposed between the peripheral electrode 33and the selector switch circuit 105.

A terminal R of the selector switch circuit 105 is connected to an inputend of the signal reception circuit 103. Also, a terminal G of theselector switch circuit 105 is connected to an earth electrode (groundelectrode).

The control circuit 101 supplies the switch circuit 104 with a controlsignal SW1 that turns the switch circuit 104 on and off. The controlcircuit 101 supplies the selector switch circuit 105 with a switchingcontrol signal SW2 that connects the movable terminal M selectively tothe terminal S, to the terminal R, or to the terminal G.

It is to be noted that, although not depicted, the voltage of thecapacitor 10 is supplied as the supply power voltage to each of thecontrol circuit 101, the signal transmission circuit 102, the signalreception circuit 103, the switch circuit 104, and the selector switchcircuit 105.

The signal reception circuit 103 processes a signal received by theperipheral electrode 33 through capacitive coupling (i.e., capacitivecoupling) with the position detection sensor of the position detectionapparatus. The signal reception circuit 103 performs processing such asdemodulation on the received signal, and forwards the processed signalto the control circuit 101.

The control circuit 101 analyzes the signal from the signal receptioncircuit 103 to determine the specifications of the position detectionapparatus, and determines the timing for signal interaction with theposition detection sensor of the position detection apparatus. Thecontrol circuit 101 then controls the format of the signal to be outputfrom the signal transmission circuit 102 in such a manner that thesignal format matches the specifications of the position detectionapparatus, and interacts with the position detection sensor at thedetermined timing.

Basically, the signal transmission circuit 102 outputs two kinds ofsignals under control of the control circuit 101: a position detectionsignal (burst signal) having a predetermined frequency for positiondetection by the position detection apparatus, and a signal thatincludes writing pressure information reflecting the writing pressuredetected by the writing pressure detection part 8. The signaltransmission circuit 102 also outputs a signal used to detect the tiltangle of the electronic pen 1. That is, under control of the controlcircuit 101, the signal transmission circuit 102 outputs the burstsignal for position detection and the burst signal for detection of thetilt angle of the electronic pen 1.

During the period in which the signal transmission circuit 102 isoutputting the burst signal for position detection, the control circuit101 performs operations to detect the writing pressure based on thecapacitance of the variable capacitor 8C formed by the writing pressuredetection part 8.

In this example, the control circuit 101 first charges the variablecapacitor 8C to full capacity. Thereafter, with the charging stopped,the variable capacitor 8C is left to discharge through the resistor R.The time is then measured from the point in time at which thedischarging is started to the point in time at which the voltage acrossthe variable capacitor 8C reaches a predetermined voltage level. On thebasis of the measured time, the capacitance of the variable capacitor 8Cat this point in time is detected. Since the capacitance of the variablecapacitor 8C corresponds to the writing pressure applied to the stylus35 at the point, the writing pressure is detected on the basis of thedetected capacitance.

The control circuit 101 converts the detected writing pressure to amultiple-bit digital signal in this example. The control circuit 101controls the signal transmission circuit 102 to output writing pressureinformation reflecting the digital signal.

In this embodiment, as depicted in FIG. 6A, the control circuit 101 in asteady state puts the electronic pen main body 3 into signal receptionmode in which to receive signals from the position detection sensor ofthe position detection apparatus. In the signal reception mode, thecontrol circuit 101 verifies reception of the signal from the positiondetection apparatus and, after performing the above-mentionedpredetermined processing, switches the electronic pen main body 3 tosignal transmission mode in which to transmit the signals to theposition detection apparatus.

In signal reception mode of this embodiment, the control signal SW1 (seeFIG. 6C) from the control circuit 101 turns off the switch circuit 104.The switching control signal SW2 from the control circuit 101 controlsthe selector switch circuit 105 to connect its movable terminal M to theterminal R (see FIG. 6D).

As a result, in the signal reception mode, the signal received by theperipheral electrode 33 from the position detection apparatus issupplied to the signal reception circuit 103 via the selector switchcircuit 105 for demodulation. The received signal thus demodulated isfed to the control circuit 101. The control circuit 101 performs theprocess of analyzing the received signal from the position detectionapparatus so as to determine the specifications of the positiondetection apparatus, as described above.

In this embodiment, the received signal from the position detectionapparatus includes information designating the timing at which theelectronic pen main body 3 is to start signal transmission. On the basisof the timing-designating information, the control circuit 101determines the timing for switching from signal reception mode to signaltransmission mode, and carries out processes such as setting of thetiming for time-division processing in signal transmission mode.Thereafter, the control circuit 101 causes the electronic pen main body3 to switch from signal reception mode to signal transmission mode.

In signal transmission mode of this embodiment, as depicted in FIG. 6B,two periods are executed on a time-division basis: a position detectionperiod Ta in which the burst signal for position detection and thewriting pressure detection information are transmitted to the positiondetection apparatus, and a tilt detection period Tb in which the tiltangle of the electronic pen 1 is detected.

In the position detection period Ta, the control signal SW1 (see FIG.6C) turns on the switch circuit 104, and the switching control signalSW2 causes the selector switch circuit 105 to connect the movableterminal M to the terminal G (see FIG. 6D). As a result, in the positiondetection period Ta, the peripheral electrode 33 is connected to theground electrode via the selector switch circuit 105. In the positiondetection period Ta, the control circuit 101 controls the signaltransmission circuit 102 to output both the burst signal for positiondetection and the writing pressure information. The position detectionsignal and the writing pressure information output from the signaltransmission circuit 102 are supplied to the stylus 35 via the switchcircuit 104, before being transmitted to the position detection sensor.In this case, the control circuit 101 causes the signal transmissioncircuit 102 to transmit from the stylus 35 the writing pressureinformation at the end of a burst signal transmission period.

At this point, the peripheral electrode 33 is connected to the groundelectrode. This allows the stylus 35 to be shielded except for its pentip part 35 a. As a result, the signal from the signal transmissioncircuit 102 is transmitted from the pen tip part 35 a of the stylus 35without being affected externally.

Next in the tilt detection period Tb, the control signal SW1 (see FIG.6C) turns off the switch circuit 104, and the switching control signalSW2 causes the selector switch circuit 105 to connect the movableterminal M to the terminal S (see FIG. 6D). In the tilt detection periodTb, the control circuit 101 controls the signal transmission circuit 102to output the burst signal for tilt detection. In this example, the tiltdetection burst signal has the same frequency as that of the positiondetection burst signal.

In the tilt detection period Tb, the tilt detection burst signal fromthe signal transmission circuit 102 is thus supplied to the peripheralelectrode 33 via the selector switch circuit 105, before beingtransmitted to the position detection sensor. Upon reception of the tiltdetection burst signal via the position detection sensor, the positiondetection apparatus detects the tilt angle of the electronic pen 1 inthe manner to be described below.

Circuit Configuration Examples of the Position Detection Apparatus

Explained next are circuit configuration examples of the positiondetection apparatus and position detection sensor. FIG. 7 is a blockdiagram for explaining a configuration example of a reception processingcircuit in a position detection apparatus 200 operated by thecapacitance method, wherein the reception processing circuit processesthe signal received from the electronic pen 1.

The position detection apparatus 200 of this example is constituted by aposition detection sensor 210 and by a pen detection circuit 220connected therewith as depicted in FIG. 7. In this example, the positiondetection sensor 210 is configured with a first conductor group and asecond conductor group. The first conductor group includes multiplefirst conductors 211Y₁, 211Y₂, . . . , 211Y_(m) (m is an integer of atleast 1) each of which is extended horizontally (X-axis direction) andwhich are spaced a predetermined distance apart in an array in parallelwith each other in the Y-axis direction. The second conductor groupincludes multiple second conductors 212X₁, 212X₂, . . . , 212X_(n) (n isan integer of at least 1) each of which is extended vertically (Y-axisdirection) and which are spaced a predetermine distance apart in anarray in parallel with each other in the X-axis direction.

It is to be noted that, in the description that follows, when there isno need to distinguish each of the multiple first conductors forming thefirst conductor group or each of the multiple second conductors formingthe second conductor group, they will be referred to as the firstconductors 211Y or the second conductors 212X.

A pen detection circuit 220 includes a selection circuit 221 acting asan input/output interface with the position detection sensor 210, anamplification circuit 222, a band-pass filter 223, a detection circuit224, a sample hold circuit 225, an AD (Analog to Digital) conversioncircuit 226, and a control circuit 227.

The selection circuit 221 selects a single conductor 211Y or 212X fromthe first conductor group or from the second conductor group on thebasis of a control signal from the control circuit 227. The conductorselected by the selection circuit 221 is connected to the amplificationcircuit 222. The signal sent from the electronic pen 1 (i.e., from itselectronic pen main body 3) and detected by the selector conductor isamplified by the amplification circuit 222. The output of theamplification circuit 222 is supplied to the band-pass filter 223, andonly the frequency component corresponding to the signal transmittedfrom the electronic pen 1 is extracted.

An output signal from the band-pass filter 223 is detected by thedetection circuit 224. An output signal from the detection circuit 224is fed to the sample hold circuit 225 that sample-holds the signal bythe sampling signal from the control circuit 227 before conversion to adigital value by the AD conversion circuit 226. Digital data from the ADconversion circuit 226 is read and processed by the control circuit 227.

The control circuit 227 outputs control signals to the sample holdcircuit 225, the AD conversion circuit 226, and the selection circuit221. Also, given the digital data from the AD conversion circuit 226,the control circuit 227 calculates the coordinates of that position onthe position detection sensor 210 which is pointed to by the electronicpen 1, and detects writing pressure information.

The control circuit 227 further detects the tilt angle of the electronicpen 1 in the manner to be described below. A method of detecting thetilt angle of the electronic pen 1 with the position detection apparatus200 is explained hereunder with reference to FIG. 8.

When the stylus 35 of the electronic pen main body 3 of the electronicpen 1 is perpendicular to an input surface of the position detectionsensor 210 as depicted in FIG. 8A, capacitive coupling occurs betweenthe pen tip part 35 a of the stylus 35 and the position detection sensor210 in a position detection period Ta. An area OBa where the capacitivecoupling takes place has the shape of a perfect circle as depicted inFIG. 8B. On the other hand, in a tilt detection period Tb, capacitivecoupling occurs between the peripheral electrode 33 and the positiondetection sensor 210. An area OBb where the capacitive coupling takesplace has the shape of a ring as illustrated in FIG. 8C.

When the stylus 35 of the electronic pen main body 3 of the electronicpen 1 is tilted relative to the input surface of the position detectionsensor 210 as depicted in FIG. 8D, the area OBa where capacitivecoupling occurs between the pen tip part 35 a of the stylus 35 and theposition detection sensor 210 in the position detection period Ta isalso shaped approximately as a perfect circle as illustrated in FIG. 8E.On the other hand, the area OBb where capacitive coupling takes placebetween the peripheral electrode 33 and the position detection sensor210 in the tilt detection period Tb has the shape of an ellipse thatreflects the tilt angle and that is elongated in the tilt direction asdepicted in FIG. 8F.

As a result, the control circuit 227 of the position detection apparatus200 is able to detect the magnitude of the tilt angle of the electronicpen 1 based on the length of the elliptic shape in a major axisdirection of the area OBb depicted in FIG. 8F. Also, the control circuit227 can detect the tilt direction of the electronic pen 1 by detectingthe major axis direction of the elliptical shape of the area OBb thatoriginates from the position pointed to by the electronic pen 1 anddepicted in FIG. 8E.

It is to be noted that, in the above example, the peripheral electrode33 used for detecting the tilt angle utilizes a signal having the samefrequency as that of the signal supplied to the stylus 35.Alternatively, the frequency of the signal supplied to the stylus 35 maybe different from the frequency of the signal fed to the peripheralelectrode 33. In such a case, the position detection apparatus 200 candistinguish between the signal from the stylus 35 and the signal fromthe peripheral electrode 33. This makes it unnecessary to execute theposition detection period Ta and the tilt detection period Tb on atime-division basis in the electronic pen main body 3 of the electronicpen 1 as described above. Instead, the signal from the stylus 35 and thesignal from the peripheral electrode 33 may be transmittedsimultaneously to the position detection sensor 210.

Effects of the First Embodiment

When the electronic pen 1 of the first embodiment is in use, with thepen tip side of the electronic pen main body 3 projected from theopening 2 b of the pen housing 2 of the electronic pen 1, not only thepen tip part 35 a of the stylus 35 but also a portion of the taperedpart 33 b of the peripheral electrode 33 on the pen tip side isprojected from the opening 2 b of the pen housing 2.

As a result, with the electronic pen 1 of the first embodiment, adistance not only from the pen tip part 35 a of the stylus 35 but alsofrom the tapered part 33 b of the peripheral electrode 33 on the pen tipside to the input surface of the position detection sensor 210 isshortened, with the capacitive coupling (capacitive coupling)strengthened therebetween. Also, because the pen tip side of theperipheral electrode 33 is the tapered part 33 b in this embodiment, thecross-sectional area of the pen tip side is made smaller. This permitsmore strengthened capacitive coupling with the position detection sensor210.

Consequently, the electronic pen 1 of the first embodiment having athinner shape profile can still establish strong capacitive couplingwith the position detection sensor 210. This enables the positiondetection apparatus 200 to detect with high sensitivity the positionpointed to by the electronic pen 1 on the position detection apparatus200. Furthermore, with the electronic pen main body 3 of the electronicpen 1 in the first embodiment, the signal received from the positiondetection apparatus 200 by the peripheral electrode 33 defines thetiming at which the electronic pen main body 3 starts transmittingsignals. In this manner, the position detection apparatus can predictwhen signals are transmitted from the electronic pen main body 3 of theelectronic pen 1 and wait for such signals. This enable good performancedespite the fact that capacitive coupling is lower in coupling strengththan electromagnetic induction coupling.

In the above-described first embodiment, the electronic pen main body 3is configured to be replaceable with a commercially available ballpointrefill. Thus, by replacing the electronic pen main body 3 with acommercially available ballpoint pen in the pen housing 2 of theelectronic pen 1, the electronic pen 1 can be used as a writingimplement.

Second Embodiment

The electronic pen of a second embodiment is a variation of the firstembodiment. In the above-described first embodiment, a single electronicpen main body 3 is housed inside the pen housing 2 of the electronic pen1. In the second embodiment, by contrast, multiple electronic pen mainbodies are housed inside the pen housing of the electronic pen. A knockmechanism is actuated to select one of the multiple electronic pen mainbodies. The pen tip of the selected electronic pen main body isprojected from the opening of the housing on the pen tip side.

As described above, the electronic pen main body 3 of the electronic pen1 in the first embodiment is configured to be replaceable with theballpoint refill 6. There is a multicolor ballpoint pen as acommercially available ballpoint pen furnished with multiple refills ofdifferent ink colors. The second embodiment provides an electronic penhaving the electronic pen main body 3 housed in a pen housing similar tothat of the multicolor ballpoint pen.

FIG. 9 is a configuration diagram depicting an appearance of anelectronic pen 1M in the second embodiment. The example in FIG. 9 isalso the electronic pen 1M configured with a pen housing 2M of atransparent synthetic resin that allows the inside to be seen through.

The pen housing 2M of the electronic pen 1M has a configurationsubstantially similar to that of the housing of a commercially availableknock type multicolor ballpoint pen and that of the knock mechanism.What is different from the housing of the commercially available knocktype multicolor ballpoint pen and the knock mechanism, as in the case ofthe pen housing 2 of the electronic pen 1 of the first embodiment andthe knock cam mechanical part 4, is how charging electrodes 2Md and 2Meare disposed in the pen housing 2M and how the fitting part of the knockmechanism is fitted to the electronic pen main body 3. It is to be notedthat, in the example of FIG. 9, three electronic pen main bodies 3BK,3R, and 3E are housed in the pen housing 2M.

The electronic pen main bodies 3BK, 3R, and 3E are each configured to beexternally similar to the electronic pen main body 3 of the firstembodiment, except that they are dimensionally the same as multicolorballpoint refills. It is to be noted that the electronic pen main bodies3BK, 3R, and 3E of the second embodiment are in the main body housing 30which, in addition to the above-described signal transmission circuit,incorporates electronic circuit components including an IC and itsperipheral circuits for implementing a function of transmitting the penmain body's identification information to the position detectionapparatus. The remaining configurations of the electronic pen mainbodies 3BK, 3R, and 3E are similar to those of the electronic pen mainbody 3 of the first embodiment.

The knock mechanism of the electronic pen 1M is furnished with knockingrods 42BK, 42R and 42E fitted, respectively, to the electronic pen mainbodies 3BK, 3R, and 3E. The fitting parts of the knocking rods 42BK,42R, and 42E are configured similarly to the fitting part 43 a of theknock cam mechanical part 4 in the first embodiment.

When one of the knocking rods 42BK, 42R, and 42E is slid toward the pentip side, the pen tip part 35 a of one of the electronic pen main bodies3BK, 3R, and 3E is projected, along with a portion of the peripheralelectrode 33. This permits capacitive coupling with the positiondetection sensor of the position detection apparatus.

In this embodiment, the position detection apparatus for use inconjunction with the electronic pen main bodies 3BK, 3R, and 3E has afunction of receiving and identifying the identification informationsent from each of the electronic pen main bodies 3BK, 3R, and 3E. Thatis, the position detection apparatus in this embodiment distinguishesbetween the electronic pen main bodies 3BK, 3R, and 3E and allows eachof them to implement a function assigned thereto.

In this example, the electronic pen main body 3BK of this embodiment isassigned the function of displaying in black the writing path (i.e.,characters or drawings) in a manner reflecting the pointed positions.The electronic pen main body 3R is assigned the function of displayingin red the writing path in a manner reflecting the pointed positions.The electronic pen main body 3E is assigned the function of erasing thewriting path input so far through pointing, according to the pointedpositions.

The position detection apparatus recognizes the identificationinformation included in the signal transmitted from each of theelectronic pen main bodies 3BK, 3R, and 3E. The position detectionapparatus then supplements the coordinate information regarding theposition pointed to by the detected electronic pen main body 3BK, 3R, or3E with information regarding the color of the writing path or theerasure thereof in accordance with the identification information,before feeding the supplemented information to a personal computerhaving a display screen, for example. It is to be noted that thefunctions assigned to the electronic pen main bodies are not limited tothose of representing the colors in which to display the writing pathreflecting the pointed position as in this example; the assignedfunctions may also involve designating the thickness of the writing pathor the types of the displayed lines such as a solid line, a dotted line,and a dashed line.

It is to be noted that, in the case of the electronic pen 1M in thesecond embodiment, multiple electronic pen main bodies 3 are housedinside the pen housing 2M. That means the axial direction of each of theelectronic pen main bodies 3 is not aligned with an opening 2Ma of thepen housing 2M. For this reason, when the knock mechanism is actuated toproject the pen tip part of one of the multiple electronic pen mainbodies 3 from the opening 2Ma of the pen housing 2M, the projectedelectronic pen main body 3 is slightly bent relative to the fitting partof the pen housing 2M.

However, since the main body cylindrical part 31 of the electronic penmain body 3 in this embodiment is furnished with the resin pipe part 31b, the elasticity of the resin pipe part 31 b permits the bending of theelectronic pen main body 3 when the tip part of the electronic pen mainbody 3 is projected. In a case where the mechanism of the multicolorballpoint pen housing such as that of the second embodiment is to beaddressed, the length of the resin pipe part 31 b in the axial directionmay be adjusted in such a manner as to let the resin pipe part 31 bsuitably absorb the bending of the electronic pen main body 3 when itstip part is projected.

It is to be noted that the second embodiment is configured such that thethree knocking rods 42BK, 42R, and 42E all have the conductor-equippedfitting parts that are fitted to the electronic pen main bodies 3.Alternatively, at least one of the multiple knocking rods may beconfigured to have the conductor-equipped fitting part to be fitted tothe electronic pen main body 3; the other knocking rods may beconfigured with conductor-free fitting parts for use with ballpointrefills.

While the second embodiment is described as an example involving threeknocking rods, there may be two, or four, or more than four knockingrods instead.

Third Embodiment

The electronic pen main body 3B of a third embodiment is configureddifferently from the electronic pen main body 3 of the above-describedfirst and second embodiments in terms of how the main body is fitted tothe pen housing of the electronic pen. The other aspects of theconfiguration of the third embodiment are similar to those of the firstand second embodiments. Thus, the fitting part disposed in the penhousing 2B of an electronic pen 1B and fitted to the electronic pen mainbody 3B of the third embodiment is configured differently from theabove-described first and second embodiments.

FIG. 10 is a set of diagrams depicting a configuration example of theelectronic pen main body 3B of the third embodiment. FIGS. 10A and 10Cdepict a first example and a second example of the electronic pen mainbody 3B of this embodiment, respectively. The first and second exampleshere are configured differently from each other only in terms of how themain body is fitted to the fitting part of the pen housing 2B of theelectronic pen 1B in the third embodiment. The other aspects of theconfiguration of the first and second examples are substantially similartherebetween. In the description that follows, the parts similar tothose of the electronic pen main body 3 in the above-described first andsecond embodiments are designated by like reference signs, and theseparts will not be discussed further in detail.

Also, FIG. 11A depicts a configuration example of the electronic pen 1Bof the third embodiment to which the electronic pen main body 3B of thisembodiment is fitted. FIG. 11A illustrates a state in which the pen tipside of the electronic pen main body 3B of the electronic pen 1B in thethird embodiment is projected from the opening of the pen housing 2B.This configuration corresponds to what is depicted in FIG. 1B regardingthe electronic pen 1 of the above-described first embodiment.

The pen housing 2B of the electronic pen 1B in the third embodiment isequipped with a fitting part 43 ap to which the electronic pen main body3B of this embodiment is fitted, as depicted in FIG. 11. A side switch2S is disposed on the side surface of the pen housing 2B. Also, aconductor band 2 f is disposed on that position of the pen housing 2Bwhich is gripped by the user upon use. These aspects of theconfiguration are different from those of the electronic pen 1 of thefirst embodiment; the remaining aspects are similar. The side switch 2Shas the configuration of a pushbutton switch or a slide switch, whereinthe configuration is well known for electronic pens and thus notdiscussed further hereunder in detailed examples.

The electronic pen 1B of the third embodiment transmits operationinformation regarding the side switch 2S to the electronic pen main body3B via the fitting part 43 ap. In addition to the position detectionsignal and the writing pressure information, the electronic pen mainbody 3B of the third embodiment transmits the operation informationregarding the side switch 2S to the position detection apparatus. Theposition detection apparatus has a function of processing the operationinformation regarding the side switch 2S. In response to the operationinformation regarding the side switch 2S received from the electronicpen main body 3B, the position detection apparatus performs processingcorresponding to the relevant function provided therein.

Also, the conductor band 2 f is constituted by a cylindrical body madeof, for example, an electrically conducting material such as aconductive rubber that partially covers the outer circumference of thepen housing 2 in the axial direction. In the third embodiment, theconductor band 2 f is configured to be connected to the ground electrodeof the electronic pen main body 3B via the fitting part 43 ap. When theuser grips the conductor band 2 f upon use, the conductor band 2 f andthe ground electrode of the electronic pen main body 3B connectedtherewith (also connected with the metal pipe part 31 a of the main bodycylindrical part 31) are connected to ground (i.e., grounded) throughthe user's body.

Also in the electronic pen main body 3B of the embodiment, as depictedin FIGS. 10A and 10C, on the pen tip side of the main body cylindricalpart 31, the pen tip side of the main body housing 30 of the electronicpen main body 3B coupled with the peripheral electrode 33 via thecylindrical coupling member 32 is capped with the front cap 34. Throughthe opening of the front cap 34, the stylus 35 is inserted and fitted.As with the electronic pen main body 3 of the above-described first andsecond embodiments, the hollow space in the main body housing 30 housesthe stylus holding member 7, the writing pressure detection part 8, theprinted-circuit board 9 including the signal transmission circuit, andthe capacitor 10 as an example of the electrical storage element forsupplying the supply power voltage, which are arrayed in the axialdirection.

Also, in the electronic pen main body 3B of the third embodiment, themain body cylindrical part 31 is constituted by the metal pipe part 31 aand the resin pipe part 31 b coupled with each other. The rear end ofthe resin pipe part 31 b is furnished with a connector, which is aconnector plug 50 in this example and fitted to the fitting part 43 apdisposed in the pen housing 2B of the electronic pen 1B.

The connector plug 50 is electrically connected to the capacitor 10 andto the electronic circuits formed on the printed-circuit board 9 insidethe electronic pen main body 3B. The connector plug 50 has multipleterminal parts, which are five terminal parts 51 a, 52 a, 53 a, 54 a,and 55 a in this example and insulated from each other.

In the electronic pen main body 3B of the first example in FIG. 10A, thefive terminal parts 51 a, 52 a, 53 a, 54 a, and 55 a of the connectorplug 50 are configured as explained hereunder. That is, in this example,the terminal part 51 a is constituted by a conductive metal forming ashaft at the center. In the example in FIG. 10A, the connector plug 50is formed by the cylindrical terminal parts 52 a, 53 a, 54 a, and 55 acombined concentrically with respect to a rod-like conductive metal ofthe terminal part 51 a, wherein each of the cylindrical terminal partshas an insulating layer formed on its inner wall surface.

In this case, the terminal part 51 a of the conductive metalconstituting the center shaft forms a tip part in the axial direction.The terminal part 51 a has its circular periphery and its tip exposed bya predetermined length in the axial direction. Also, the cylindricalterminal parts 52 a, 53 a, 54 a, and 55 a each have its circularperiphery exposed by a predetermined length in the axial direction. Thatmeans the five terminal parts 51 a, 52 a, 53 a, 54 a, and 55 a of theconnector plug 50 each have its circular conductive contact part exposedat a different position in the axial direction. It is to be noted thatthe terminal part 51 a, shaped cylindrically, has its circularperipheral side surface and its tip portion forming a conductive contactpart.

The connector plug 50 is inserted into a fitting recessed part of aconnector jack 90 formed in the fitting part 43 ap disposed on therotator 43 in the hollow space of the pen housing 2B of the electronicpen 1B. This creates a state in which the connector plug 50 iselastically connected to each of five contact terminals 91, 92, 93, 94,and 95 disposed on the connector jack 90, as depicted in FIG. 10B. Thefive contact terminals 91, 92, 93, 94, and 95, each made of a conductiveelastic metal, are connected electrically to the charging electrodes 2 dand 2 e, the side switch 2S, and the conductor band 2 f disposed on thepen housing 2B (see FIG. 11B).

When the connector plug 50 is thus inserted to and coupled with theconnector jack 90, the electronic circuit components inside theelectronic pen main body 3B are electrically connected to those in thepen housing 2B of the electronic pen 1B. FIG. 11B schematically depictssome typical electronic circuit components disposed in the pen housing2B of the electronic pen 1B and connected electrically to electricalcircuit components inside the electronic pen main body 3B when theconnector plug 50 is inserted to and coupled with the connector jack 90.

In the example of FIG. 11B, the terminal parts 51 a, 52 a, 53 a, 54 a,and 55 a of the connector plug 50 are each connected electrically to thecharging electrodes 2 e and 2 d, to both ends 2Sa and 2Sb of the sideswitch 2S, and to the conductor band 2 f via the five contact terminals91, 92, 93, 94, and 95 (not depicted in FIG. 11B) disposed on theconnector jack 90.

In this case, the circular conductive contact parts of the terminalparts 51 a, 52 a, 53 a, 54 a, and 55 a of the connector plug 50 areconnected respectively to the contact terminals 91, 92, 93, 94, and 95of the connector jack 90. As a result, even when the electronic pen mainbody 3B is rotated around its center line in the axial direction, theelectrical connection is continuously maintained and electricaldisconnection can be averted.

In the second example of the electronic pen main body 3B in FIG. 10C,five terminal parts 51 b, 52 b, 53 b, 54 b, and 55 b of the connectorplug 50 are configured as described hereunder. The connector plug 50 ofthis example has a configuration similar to that of pin plugs for audiopurposes (e.g., 5-pin plugs with a noise cancelling function). In thisexample, the five terminal parts 51 b, 52 b, 53 b, 54 b, and 55 b havetheir circular conductive contact parts of the same diameter exposed atdifferent positions in the axial direction.

That is, the terminal part 51 b, which is the most projected tip end ofthe five terminal parts 51 b, 52 b, 53 b, 54 b, and 55 b, serves as atip terminal. The intermediate three terminal parts 52 b, 53 b, and 54 bserve as ring terminals insulated from one another by means ofinsulating rings 56 a, 56 b, 56 c, and 56 d. The terminal part 55 b atthe base side of the electronic pen main body 3B serves as a sleeveterminal.

As in the case of FIG. 10B, the connector jack 90 coupled with theconnector plug 50 of the electronic pen main body 3B in FIG. 10C hasfive contact terminals that come into contact with the circularconductive contact parts of the five terminal parts 51 b, 52 b, 53 b, 54b, and 55 b to establish electrical connection. Consequently, thecoupling of the connector jack 90 with the connector plug 50 of theelectronic pen main body 3B of the second example in FIG. 10C is similarto that in the first example.

It is to be noted that, in the above examples, the connector plug isdisposed at the rear end of the main body cylindrical part 31 of theelectronic pen main body 3B opposite to the pen tip side, with theconnector jack arranged at the fitting part 43 ap of the pen housing 2B.Alternatively, the connector jack may be disposed at the rear end of themain body cylindrical part 31 of the electronic pen main body 3Bopposite to the pen tip side, with the connector plug arranged at thefitting part 43 ap of the pen housing 2B.

It is to be noted that, obviously, the connector structure in the thirdembodiment can also be applied to the multicolor ballpoint pen in thesecond embodiment. In such a case, respective side switches may bearranged to correspond to multiple electronic pen main bodies to befitted to the multiple fitting parts of the pen housing. Alternatively,a single side switch may be provided for shared use by the multipleelectronic pen main bodies. Obviously, in a case where one of themultiple fitting parts of the pen housing is appropriated for use withthe electronic pen main body, with the remaining fitting parts used inconjunction with ballpoint refills, it is sufficient to provide one sideswitch for use with the single electronic pen main body.

Other Embodiments

FIG. 12 depicts other embodiments of the electronic pen main body. FIG.12A depicts a variation of the electronic pen main body 3 of theabove-described first embodiment. As with the first embodiment, thisvariation is configured to be replaceable with the ballpoint refill 6.In the electronic pen main body 3C of this embodiment, the parts similarto those of the first embodiment are designated by like reference signs,and these parts will not be discussed further in detail.

The electronic pen main body 3C of this embodiment uses a peripheralelectrode 33C shaped differently from the peripheral electrode 33 of theelectronic pen main body 3 of the first embodiment. That is, as depictedin FIG. 12A, the peripheral electrode 33C of the electronic pen mainbody 3C of this embodiment is given a cylindrical shape with its outerdiameter kept constant in the axial direction, wherein the outerdiameter is the above-mentioned diameter R1 (see FIG. 2) smaller thanthe diameter of the opening 2 b of the electronic pen housing 2.

Because the peripheral electrode 33C of the electronic pen main body 3Cof this embodiment is configured differently from that of the electronicpen main body 3 of the first embodiment, a cylindrical coupling member32C for coupling the peripheral electrode 33C with the main bodycylindrical part 31 is configured to couple the peripheral electrode33C, in a manner according to the structure of the peripheral electrode33C, with the main body cylindrical part 31 via a ring-shaped flangepart 32CF. Also, a front cap 34C is configured differently to correspondto the configuration of the peripheral electrode 33C. The otherconfigurations are similar to those of the electronic pen main body 3 ofthe first embodiment.

The electronic pen main body 3C of the example in FIG. 12A can also behoused inside the pen housing 2 of the electronic pen 1, with the resinpipe part 31 b of the main body cylindrical part 31 fitted to thefitting part 43 a. Pressing the knocking rod 42 of the knock cammechanical part 4 causes the pen tip part 35 a of the stylus 35 on thepen tip side of the electronic pen main body 3C, the front cap 34C, anda portion of the peripheral electrode 33C on the pen tip side to projectfrom the opening 2 b.

As a result, the electronic pen main body 3C of the example in FIG. 12Acan also provide advantageous effects similar to those of the electronicpen main body 3 of the first embodiment. Upon use, the stylus 35, thefront cap 34C, and a portion of the peripheral electrode 33C on the pentip side are projected to the outside from the opening of the electronicpen housing 2C as indicated by a dotted line in FIG. 10A. In this case,the cylindrical part with a constant outer diameter of the peripheralelectrode 33C is positioned at the opening of the housing 2C. This makesit easy to adjust the outer diameter of the cylindrical part of theperipheral electrode 33C such that the pen tip side of the electronicpen main body 3C will not rattle in the opening of the housing 2C.

Next, the example depicted in FIG. 12B is also another variation of theelectronic pen main body 3 of the above-described first embodiment. Themain body cylindrical part 31D and a cylindrical coupling member 32D ofthe electronic pen main body 3D in this embodiment are configured to bedifferent from those of the electronic pen main body 3 of the firstembodiment; the remaining configurations are similar. Thus, those partsof the electronic pen main body 3D in this embodiment that are alsosimilar to those in the first embodiment are designated by likereference signs in the ensuing description, and these parts will not bediscussed further in detail.

The main body cylindrical part 31D of the electronic pen main body 3D inthis embodiment has an outer diameter R3 larger than the outer diameterR2 of the main body cylindrical part 31 of the electronic pen main body3 in the first embodiment. The main body cylindrical part 31D of theelectronic pen main body 3D in this embodiment has an inner diameteralso larger than that of the main body cylindrical part 31 of theelectronic pen main body 3 in the first embodiment.

Because the electronic pen main body 3D in this embodiment has the mainbody cylindrical part 31D configured differently from that of theelectronic pen main body 3 in the first embodiment, the cylindricalcoupling member 32D for coupling the peripheral electrode 33 with themain body cylindrical part 31D is configured to couple the peripheralelectrode 33 with the main body cylindrical part 31D via a ring-shapedflange part 32DF in a manner according to the configuration of the mainbody cylindrical part 31D.

As described above, a large hollow space is provided in the main bodycylindrical part 31D of the electronic pen main body 3D of thisembodiment. Given the large hollow space in the main body cylindricalpart 31D, the electronic pen main body 3D of this embodiment isconfigured to hold a primary cell (battery) 10BT in its hollow space inplace of the capacitor 10 used as the electrical storage element by theelectronic pen main body 3 in the first embodiment, as depicted in FIG.12B. The other electrical circuit components of the main bodycylindrical part 31D are housed therein in a manner similar to the firstembodiment; these components are fed with necessary supply powervoltages from the primary battery 10BT.

As a result, the electronic pen main body 3D of this embodiment has noneed for a configuration enabling the capacitor 10 to be charged fromthe outside. In this example, the main body cylindrical part 31D is madeof a metal pipe, of which the rear end, opposite to the pen tip side, isfitted detachably with a closing cap 31De. The electronic pen main body3D of this embodiment is configured to let the primary battery 10BThoused in the main body cylindrical part 31D be replaced, out of themain body cylindrical part 31D by removing the closing cap 31De. As withthe above-described embodiments, the main body cylindrical part 31D mayalternatively be configured using the metal pipe part coupled with theresin pipe part.

The electronic pen housing that holds the electronic pen main body 3D inthis embodiment is configured differently from the electronic penhousing of the above-described embodiments. That is, even in a casewhere a housing including the knock cam mechanism or the knock mechanismis used as the electronic pen housing for this electronic pen main body3D as with the above-described embodiments, the fitting part of theelectronic pen housing which is fitted to the electronic pen main body3D has no need for electrical configurations. Still, it is to be notedthat as with the above-described embodiments, the pen tip side of thehousing has an opening with a diameter larger than the diameter R1 andthat the pen tip part 35 a of the stylus 35 on the pen tip side of theelectronic pen main body 3D, the front cap 34, and a portion of theperipheral electrode 33 on the pen tip side are projected to the outsidefrom the opening of the housing upon use.

In addition, there are a well-known variety of types of ballpointrefills in addition to the resin pipe with a thin ink storage part asdepicted in FIG. 2A. There also is a cartridge type with a thick inkstorage part such as the main body cylindrical part 31D of theelectronic pen main body 3D of this example. The electronic pen mainbody 3D of this embodiment can also be attached to the housing of thatcartridge type ballpoint pen.

It is to be noted that, also in a case where the main body cylindricalpart 31D is configured to be thick as with the electronic pen main body3D of this embodiment, the primary battery 10BT in the hollow space ofthe main body cylindrical part 31D may be replaced with an electricalstorage element such as a secondary battery or a capacitor. Also in thiscase, the rear end of the main body cylindrical part 31D may beconfigured similarly to the electronic pen main body 3 of the firstembodiment or to the electronic pen main body 3B of the thirdembodiment.

The electronic pen using the electronic pen main body 3C of the examplein FIG. 12B can also provide advantageous effects similar to those ofthe electronic pen 1 of the first embodiment. Upon use, the stylus 35,the front cap 34, and a portion of the tapered part of the peripheralelectrode 33 on the pen tip side are projected to the outside from theopening of the electronic pen housing 2D as indicated by a dotted linein FIG. 12B.

FIG. 12C depicts a variation of the electronic pen main body 3C in FIG.12A. The peripheral electrode 33C′ of the electronic pen main body 3C′of the example in FIG. 12C differs from the peripheral electrode 33C ofthe electronic pen main body 3 of the example in FIG. 12A in that thepen tip side has a tapered part 33C′b. That is, the peripheral electrode33C′ of the electronic pen main body 3C′ of this example is shaped suchthat a tapered part 33C′b is formed on the pen tip side of a cylindricalpart 33C′a having the diameter R1 smaller than the diameter R0 of theopening 2 b of the electronic pen housing 2 (see FIG. 1). In thisexample, a front cap 34C′ is formed at the tip of the tapered part 33C′bof the peripheral electrode 33C′. The other configurations are the sameas those of the electronic pen main body 3C of the example in FIG. 12A.

Also in the case of the electronic pen main body 3C′ of the example inFIG. 12C, the stylus 35, the front cap 34C′, and a portion of theperipheral electrode 33C′ on the pen tip side are projected to theoutside from the opening of the housing 2C of the electronic pen. Inthis case, the portion of the peripheral electrode 33C′ projectedexternally includes not only the tapered part 33C′b but also a portionof the cylindrical part 33C′a, with the cylindrical part 33C′apositioned at the opening of the housing 2C. This provides advantageouseffects similar to those of the example in FIG. 12A.

Other Embodiments and Variations

In the above description of the embodiments, the electronic pen mainbody is configured to be replaceable with a ballpoint refill as awriting instrument. Obviously, the electronic pen main body may beconfigured alternatively for dedicated use as the electronic pen.

Although the above-described embodiments are configured such that theelectronic pen main body is inserted to and retracted from the housingby the knock mechanism, the electronic pen main body is not limited tothe knock type. Alternatively, the electronic pen main body may simplybe housed inside the pen housing. In this case, the pen tip side of theelectronic pen main body is always projected from the opening of the penhousing. The projected pen tip side may then be protected by a screw-onor press-fit cap fitted to the pen housing to cover the pen tip side ofthe electronic pen main body.

It has been explained that the peripheral electrode is configured with acylindrical conductor. Alternatively, the peripheral electrode may beconfigured with multiple conductors divided along the circumferentialdirection that collectively form a cylindrical shape.

It has also been explained that the stylus 35 is configured with aconductive metal. Alternatively, any suitable conductive material may beused to form the stylus 35. For example, the stylus 35 may be configuredusing a hard resin mixed with conductor powder.

It is to be noted that the main body cylindrical part of the electronicpen main body may be configured using not the metal pipe part and theresin pipe part coupled with each other but a single metal pipe or asingle resin pipe. In a case where the main body cylindrical part isconfigured with one metal pipe and where the main body cylindrical partneeds to be electrically connected with electronic components inside thehousing, a member equipped with a conductor for electrical connection isprovided to the rear end of the main body cylindrical part opposite tothe pen tip side, with an insulator such as a resin interposed betweenthe member and the cylindrical part.

DESCRIPTION OF REFERENCE SYMBOLS

-   -   1 Electronic pen    -   2 Electronic pen housing    -   3 Electronic pen main body    -   4 Knock cam mechanism    -   7 Stylus holding member    -   8 Writing pressure detection part    -   9 Printed-circuit board    -   10 Capacitor for electrical storage    -   10BT Primary battery    -   30 Housing of electronic pen main body    -   31 Main body cylindrical part    -   32 Cylindrical coupling member    -   33 Peripheral electrode    -   34 Front cap    -   35 Center electrode (stylus)

1. An electronic pen main body allowing at least a pen tip of anelectronic pen to be housed in a cylindrical housing of the electronicpen in such a manner as to be projectable from one opening of thecylindrical housing in an axial direction, the electronic pen main bodycomprising: a conductive center electrode of which one end in the axialdirection forms the pen tip; and a peripheral electrode disposed aroundthe center electrode except at least for the pen tip, the peripheralelectrode being insulated from the center electrode, wherein, when theone end of the center electrode forming the pen tip is projected to theoutside from the opening of the cylindrical housing of the electronicpen upon use, a portion of the pen tip side of the peripheral electrodeis also projected to the outside from the opening of the cylindricalhousing of the electronic pen.
 2. The electronic pen main body accordingto claim 1, wherein the pen tip side of the peripheral electrode has atapered shape.
 3. The electronic pen main body according to claim 1,further comprising: a main body cylindrical part incorporating a signaltransmission circuit generating a signal supplied at least to the centerelectrode, wherein the peripheral electrode is coupled with the pen tipside of the main body cylindrical part in the axial direction, and themain body cylindrical part is not projected to the outside from theopening of the cylindrical housing of the electronic pen.
 4. Theelectronic pen main body according to claim 3, wherein the peripheralelectrode and the main body cylindrical part coupled with each otherform a hollow space therein in which a fitting part for the centerelectrode is disposed, and the center electrode is detachably fitted tothe fitting part.
 5. The electronic pen main body according to claim 3,wherein the peripheral electrode has a diameter smaller than that of themain body cylindrical part.
 6. The electronic pen main body according toclaim 3, wherein the peripheral electrode has an anterior part and aposterior part, the anterior part being on the pen tip side andincluding the portion projected to the outside from the opening of thecylindrical housing of the electronic pen, the posterior part being onthe side coupled with the main body cylindrical part, and the anteriorpart has a tapered shape on the pen tip side and the posterior part hasa cylindrical shape with a predetermined diameter.
 7. The electronic penmain body according to claim 3, wherein the main body cylindrical partincludes a battery that supplies a supply power voltage to the signaltransmission circuit.
 8. The electronic pen main body according to claim3, wherein the main body cylindrical part includes an electrical storageelement and a terminal conductor, the electrical storage elementsupplying a supply power voltage to the signal transmission circuit, theterminal conductor allowing the electrical storage element to be chargedfrom the outside.
 9. The electronic pen main body according to claim 3,wherein the peripheral electrode is configured to be grounded so as tofunction as a shield electrode when the signal is supplied from thesignal transmission circuit to the center electrode.
 10. The electronicpen main body according to claim 3, wherein the peripheral electrode isconfigured to function as a tilt detection electrode when the signal issupplied from the signal transmission circuit to the peripheralelectrode.
 11. The electronic pen main body according to claim 3,wherein the main body cylindrical part is configured to be bendable in adirection intersecting with the axial direction.
 12. An electronic penhaving a cylindrical housing with an opening on one end thereof forminga pen tip side in an axial direction, the cylindrical housing holding atleast one electronic pen main body inside, the electronic pen main bodycomprising: a conductive center electrode of which one end in the axialdirection forms a pen tip; and a peripheral electrode disposed aroundthe center electrode except at least for the pen tip, the peripheralelectrode being insulated from the center electrode; wherein, when theone end of the center electrode forming the pen tip is projected to theoutside from the opening of the cylindrical housing upon use, a portionof the pen tip side of the peripheral electrode is also projected to theoutside from the opening.
 13. The electronic pen according to claim 12,wherein a diameter of the center electrode of the electronic pen mainbody and a diameter of the portion of the peripheral electrode projectedfrom the opening are each equal to or smaller than a diameter of a pentip part of a ballpoint refill, the electronic pen main body havingsubstantially a same length as that of the ballpoint refill.
 14. Theelectronic pen according to claim 13, wherein the cylindrical housingincludes a knock type ballpoint pen mechanism that corresponds to theelectronic pen main body or to the ballpoint refill.
 15. The electronicpen according to claim 12, wherein the cylindrical housing is configuredto hold the ballpoint refill inside and to function as a ballpoint pen.16. The electronic pen according to claim 15, wherein the cylindricalhousing includes a knock type ballpoint pen mechanism that correspondsto the electronic pen main body or to the ballpoint refill.
 17. Theelectronic pen according to claim 12, wherein the cylindrical housingholds inside a plurality of the electronic pen main bodies and a knocktype multicolor ballpoint pen mechanism allowing one of the electronicpen main bodies to be selected in such a manner that the one end of astylus part of the selected electronic pen main body is projected to theoutside from the opening.
 18. The electronic pen according to claim 17,wherein the cylindrical housing holds inside one or a plurality ofrefills of the ballpoint pen in place of one or more of the plurality ofthe electronic pen main bodies, in such a manner that the electronic penfunctions as a knock type multicolor ballpoint pen.
 19. The electronicpen according to claim 12, further comprising: a cap fitted to theopening side of the cylindrical housing to cover the pen tip sideprojected from the opening of the cylindrical housing.